The goal of this research proposal is to develop unique microarray-based assays to detect autoantibodies to glycopeptide epitopes of glycoproteins, and to evaluate their usefulness as diagnostic biomarkers for early detection of adenocarcinomas derived from different organ sites. We will also examine the expression of tumor associated glycan structures and mucin core proteins, in tissues of patients with early and late cancer. Specific Aim 1. Test the hypothesis that autoantibody responses to tumor associated glycopeptide epitopes are useful as early diagnostic or prognostic markers for cancer. We will characterize the specificities of auto- antibodies using novel mucin based O-glycopeptide /glycoprotein arrays for screening sera from breast and pancreatic cancer patients,and serial samples of sera taken before diagnosis of cancer from women subsequently developing breast, ovarian, pancreatic and other carcinomas. Specific Aim 2. Document the expression of cancer-associated mucin O-glycopeptide epitopes from early stage breast (including DCIS) and pancreatic cancer to invasive and metastatic disease, and correlate with the presence or absence of autoantibody responses to these epitopes to be analyzed as under Aim 1. Specific Aim 3. Characterize expression of tumor associated glycans and glycosyltransferases in metastatic pancreatic cancer on a series of cases in which we have primary tumor and multiple metastatic sites obtained by rapid autopsy.